Solvent fractionation of waxcontaining mixtures



Sept. 16, 1952 w. CLARKE 2,610,943

SOLVENT FRACTIONATION 0F WAX-CONTAINING MIXTURES Original Filed Sept.16, 1947 EXT/V. SOLVENT H Z'LIADDITIVE ATTEST INVFNTOR.

c} Ed ar V'. Clarke "7/10 5 KM Patented Sept. 16, 1952 SOLVENTFRAGTIQNA'IELON QEEWAX, ,QQNIAJNING MIXTURES Edgar-W. Clarita-Laurelsnringsyfl. jgyassi'gnor to The Atlantic Refinin'g"on'1 'pany,Philadelphi'a, Pa. a corporation of "Pennsylvania Ori n l applicationemb r .11 47 Seria "The present invention relates to the treatment .ofoilywaxes, and more particularly tothe separationofwax-containing-mixtures into fractions of higher and lower-meltingpoint, using aflsolvent com-prising phenol and an additive comprising"turfural. 7

This applicationis a division of ccpending application, Serial No,77%230; filed September 16, 1947, now Patent No.2;578;5;10,-andentitled-Solvent Fractionation of -"Wax"ContainingMixtures. i I

The present lnventionls especially applicable -to the deoiling of-'hydroearbon waxes containing not -more than about 70% of oil, andtothe separation of wax-mixtures of low -oilcontent into fractions ofdifferent melting point. The process of the present -in vention may beapplied -the' refining,- purification, or separation of wax stocks suchas petroleum slack wax, crude -mierocrystall inewax, paraffin waxes,petrolatum-wax, montah wax, ceresin, ozekerite, waxes from thedestructive or -non-d estructive hydrogenation of mineral oil,--synthetic hydrocarbon hi1, shale oil, coal, andwaxes produced-synthetl cally by the catzalytic-reaction of hydrocarbons, or waxesderived 'fromthe modified Fischer-Trop'sch reaction of carbon-monoxideand hydrogen. The processofithis invention is especially applicable inthe separation of wax mixtures containing color bodies-and oilinto ahigher melting wax fractionlof light color and low :oil content, and alower melting wax fraction of darker color and containing most of the..oil originally present in the-wax mixture.

"In accordance :with this invention, a .wax contamin m xtu e is sepaated int fract on o higher and lower melting point by countercurrentlycontacting the wax-containing mixture in an extraction zone with anextraction solvent and a solvent additive or additives eta-temperatusuchthat w liqu d phase ar term one comprisingthe higher melting waxfraction with minor amounts of solvent and additive, and the othercomprising the lower melting wax fraction with majoramountsof solventand additive, separating the 'liq-uid phases-from oneanother, andremoving-the solvent and additive --from each. The extraction solvent:an'd'additives employed may-have a density greater than that of thewax. However, when the additive or additives-are par- No. v774,230.Divided andltliis ,a' liplication '0'! vcmbe fi 1 4 1$ i -125,728

'3 Claims. (Cl. 1%?173 tialiy immiscible with -the extraction solventand are" less -densethan such solvent-or the wax, sthe additive-oradditives will fiow countercurrent to the extraction solventand willappear with that *liquid phase comprising the higher melting max,

traction. l h'e success' ot the process depends upon the eentrel of thetemperature throughout "the extraction gone and --upon the regulation'iof theproportiens of solvent-and additive used, and

the points of introduction of the wax-containing mixture. the solvent,and the additive into the extraction zone.

' The-extraction solve-ntmay be defined .an agent--wh-ich,-whenintimately mixed w-it-h-a waxcontaining mixture, forms twoliquid phases.or

layers, one comprising a -raffinate phase contaming mostly wa-x ofhigher melting point than the untreated--wax-and-a portion oflthesolvent, I

and the-ether comprising'an extract phase containinganostly solvent, andwax-oi, lower melting point than the untreatedwaxg as .well as ;a majorportion of the color bodies and oil orig.- lnail'ypresentintheMn-treated WaX.

" flhe solvent additivemayxbe defined as anagent used in --eonjunctionwith the extraction I solvent for the purpose "of -mod-if ying thecharacteristics of the extraction solvent. The additive may lower thetemperature at which isolid Wax precipitates out of the extractionsolvent, or it may raise the miscibility -temperature of the -BXtE3Crtion solvent-with thesvax. However, the additlve chosen -for aparticular extraction solvent must not excessively lower the selectivityof the extraction solvent at the temperature of .iex-

traction. 7

The extraction solvent --may be employed .1111 H amounts ranging irom lI to 5 -volumes of solvent per =volurne of -m t1eated wax stock, whilethe additive or additiyesmay be used in amounts ranging from--0 .05 to-l-volume-per volume -o'f.un- 'treated wax, v V The extraction solventwhich-maybe employed in accordance -with the present 5 invention comprises phenol flpreierably anh-ydrous) The solvent additive oradditives, --whieh -are usually employed {in amounts --oonstituting not-more-than '50 icyvolume'of the extraction: sol;- vent, comprisefurfura'l.

' fl he process of the present sinvention .may ,he

carried out in-a multiestagewbatch countercpr:

stood with reference to the accompanying drawing which illustratesdiagrammatically a continuous extraction system suitable for. carryingout the process. V

Referring to the drawing, a wax-containing mixture is continuouslyintroduced, inli'quid conthe solvent storage vessel 3 for reuse.

dition, into the extraction tower I through valve controlled pipe 2 at arate of 00 volumes per hour. An extraction solvent comprising phenol iscontinuously introducedfrom vessel 3 by means ,8 into the extractiontower l between the point of introduction of the first additive and theoutlet of the extract phase, at a rate of 40 volumes per hour, suchsecond additive being delivered 7 from vessel 9 by pipe 10. An intimatecountercurrent contacting of the wax stock, the extraction solvent, andthe additives is effected in tower I, a temperature gradient beingmaintained in the tower by means of coils ll through which a heating orcooling medium is circulated as required, the temperature adjacent thetop of the tower being higher than that adjacent the bottom of thetower, the contents of the tower being entirely in the liquid phase. Thewax stock,

.being subjected to'the action of the solvent and additives, is causedto separate by solvent action into two fractions, the higher meltingfraction .wax passing upwardly through the tower together .with a minoramount of dissolved extraction solvent and additive, and being withdrawntherefrom'a-bove the level of the dotted line l2 representing the highermelting wax phase relatively free of entrained, immiscible solvent andadditive.

The rafiinate phase comprising the higher melting wax and dissolvedsolvent and additive is .passed from the top of tower i throughvalvecontrolled pipe I3 into a vacuum evaporator or still l4 wherein thesolvent and additive is removed from the higher melting wax byvaporization, the solvent and additive vapors passing through pipe l5into fractionating tower [6 provided with a reboiler or heating coil I],while the higher melting wax is drawn from the bottom of evaporator l4and delivered by valve-controlled pipe I8 into storage vessel l9. Suchwax fraction was white in color, and had a substantially higher meltingpoint and a lower oil content than the wax stock originally charged. Theextract phase comprising the lower melting wax fraction, color bodies,oil, and a major portion of the extraction solvent and additives iswithdrawn from the lower section of tower l beneath the level of thedotted line 20 representingthe extract phase relatively freeofentrained,

4 higher melting wax. The extract phase is delivered by valve-controlledpipe 2! into a vacuum evaporator or still 22 wherein the solvent andadditives are vaporized from the lower melting wax, the latter beingdrawn from the bottom of the evaporator and passed by valve-controlledpipe 23 to storage Vessel 24. The lower melting wax was brown in colorand had a substantially lower melting point and a higher oil contentthan the original waxy mixture. 7.

The solvent and additive vapors are passed from the top of evaporator 22through pipe 25 into fractionating tower l6, wherein such vaporstogether with those introduced through pipe l5, are fractionated, theextraction solvent, 1. e., phenol, being drawn from the bottom of thetower as a liquid and returned by means of pipe 26 to The additive, i.e., furfural separated from the phenol by fractionation in tower i6 istaken overhead as vapor by pipe 21, condensed in condenser 28, andreturned by pipes 29 and 30 to storage vessels 6 and 9, respectively. Aportion of the condensate may be returned by pipe 3| to the top of towerI6 as reflux. f

Depending upon the temperature of operation, the firstadditive may beintroduced somewhat above the point of introduction of the liquefied waxstock, for example, by means of valve-controlled pipe 32 rather thanthrough valve-controlled pipe 1, in which case the second additive maybe admitted through either or both of valvecontrolled pipes 1 and 8below the point of introduction of the wax stock. In general, theraflinate wax phase withdrawn from the extraction tower will containfrom 5% to 25% of solvent and additive, while the extract wax phase willcontain from 55% to of solvent and additive.

In the event that the extraction is to be carried out in a multi-stagebatch countercurrent system,for example, a 4-stage system using thesolvent and additives specifically set forth above, the wax stock wouldbe introduced into the first stage extractor, the extraction solventcomprising phenol would be introduced into the fourth stage extractor,and the first additive, i. e., furfural, would be introduced into thefirst stage extractor. The second additive, e. g., furfural, would beintroduced into the second stage extractor. The extract phase iswithdrawn from the first stage extractor, while the rafiinate phasewould be removed from the fourth stage extractor. The temperature wouldincrease progressively from the first stage to the fourth stage, usingthe waxy stock, solvent, and additives described hereinabove. It is tobe understood, of course, that the quantities andcomposition of thesolvent and. of the additives may be variedwithin certain limits.

Exemplary of the solvent and additive materials which may be used inaccordance with this invention are the following, the quantities'beingvolumes per unit volume of wax stock.

ggfigg ls t Additive 2nd Additive phenol 3.51 furfural 0.4i [uriural0.43: 0.3 vols. 0.1 vols. 0.1 vols.

aerogsa's extracted ina system similar to" that shown in theaccompanying drawing, the extraction solvent comprising 3.5 volumes ofphenol,,the. first additive comprising 10.4 volume offurfural, and

the second additive comprising 014 volume of furfuralL The slack waxwasintroduced into tower I} by-pipe it; the solvent by-pipet andmanifoldifa, the first'addi-tive byp-ipe l-andthe second additive pipee. The teiriper r, ure ingthie' extraction-tower was maintaihedconstant' at 95- After countercurrent contacting and removal of therafiinate phase from the top of the tower, and the extract phase fromthe bottom of the tower, the solvent and additives were recovered fromthe wax fractions by vacuum evaporation and fractionation. The resultsare shown in the following table.

Where the extraction operation is conducted in a tower, it has beenfound that a tower having a height of about feet and a diameter of 6feet is satisfactory. The tower is provided with suitable packing toWithin about 4 feet of the top and bottom' thereof, such spacesfunctioning as quiescent zones in which entrained materials arepermitted to separate from the rafiinate and extract phases,respectively. In such a tower, the wax stock is charged at a point about13 feet from the bottom thereof, or approximately A; the distance fromthe bottom of the tower. The extraction solvent is charged just abovethe upper level of the packing, for example, 3 to 4 feet from the top ofthe tower. The first additive may be introduced adjacent the point ofintroduction of the wax stock, for example, 2 feet above or below thewax inlet. The second additive is introduced approximately 2 feet belowthe point of introduction of the first additive. These values may bealtered somewhat, depending upon the tower design, the solvent andadditives used, and the temperatures maintained at various levels in thetower. The rafiinate phase is Withdrawn from the top of the tower, andthe extract phase from the bottom thereof, the extraction solvent beingmore dense than the wax stock.

I claim:

1. The method of separating a Wax-containing mixture into fractions ofhigher and lower melting point, which comprises countercurrentlycontacting said wax-containing mixture in an extraction zone with anextraction solvent and solvent additives at a temperature such that twoimmiscible liquid phases are formed, one comprising the higher meltingwax fraction containing solvent and additives, and the other comprisingsolvent and additives and the lower melting wax fraction, separating thephases from one another, and removing the solvent and additives fromeach, the solvent being introduced into the extraction zone near thepoint of withdrawal of the higher melting wax fraction, the firstadditive being introduced adjacent the point of introduction of thewax-containing mixture, and

the second additive beingrintrodu'ced .betweenrthe-fraction}thesolventcomprising:3.2 toast-volumes of: phenol per volumeoffi wax containinglmixture. the first additivecomprising-03' to 0 .51volume; of furfural per volume of wax-containing mixture, and thes'econd additive comprising 0.3 to 0.5 volume of furfural per volume ofwax-containing mixture.

2. The method of separating awax-containing mixture into fractions ofhigher and lower melting point, which comprises countercurrentlycontacting said wax-containing mixture in an extraction zone with anextraction solvent and solvent additives at a temperature such that twoimmiscible liquid phases are formed, one comprising the higher meltingwax fraction with minor amounts of solvent and additives, and the othercomprising the lower melting wax fraction with major amounts of solventand additives, separating the phases from one another. and removing thesolvent and additives from each, the solvent being introduced into theextraction zone near the point of withdrawal of the higher melting waxfraction, the first additive being introduced between the point ofintroduction of the wax-containing mixture and the point of withdrawalof the lower melting wax fraction, and the second additive beingintroduced between the point of introduction of the first additive andthe point of withdrawal of the lower melting wax fraction, the solventcomprising 3.2 to 3.8 volumes of phenol per volume of wax-containingmixture, the first additive comprising 0.3 to 0.5 volume of furfural pervolume of wax-containing mixture, and the second additive comprising 0.3to 0.5 volume of furfural per volume of wax-containing mixture.

3. In a method of separating a wax-containing mixture into fractions ofhigher and lower melting point, wherein the wax-containing mixture iscontacted in an extraction zone with an extraction solvent and solventadditives at a temperature above the melting point but below thetemperature of complete miscibility of the mixture, the steps whichcomprise introducing 1 volume of liquefied wax-containing mixture intothe extraction zone at a point intermediate the points of withdrawal ofthe higher and lower melting Waxes including the solvent and additive,introducing 3.2 to 3.8 volumes of extraction solvent comprising phenolat a point adjacent the point of withdrawal of the higher melting waxfraction including solvent and additive, but intermediate said point ofwithdrawal and the point of introduction of the liquefied wax-containingmixture, and introducing 0.3 to 0.5 volume of an additive comprisingfurfural intermediate the point of introduction of the liquefiedwax-containing mixture and the point of withdrawal of the lower meltingwax fraction including solvent and additive, introducing 0.3 to 0.5volume of an additive comprising furfural at a point intermediate thepoint of introduction of the first additive and the point of withdrawalof the lower melting wax fraction including solvent and additive,efiecting countercurrent contact between the liquefied wax-containingmixture and the solvent and additives at a temperature such that twoimmiscible liquid phases are formed, one

phase comprising the highermelting wax fraction containing minor amountsof solvent and additives, and the other liquid phase comprising thelower melting wax fraction and major -amounts of soivent and additives,the tempera- 8 REFERENCES CITED ture in the extraction Z0118 increasingin the The following references are of record in the rection of flowofttilhe millmeirzlnelting g r: limi file 0f t i patent:

tion, separately wi draw g e respec ve qu phases from the extractionzone, and removing 5 UNITED STATES PATENTS the solvent and additivestrom each. V Number Name Date 2,017,432 Bahlke Oct. 15, 1935 EDGAR. W.CLARK-E. 2,048,513 Page July 21, 1936 2,141,361 Pilat et a1 Dec. 27,1938 2,160,930 Whiteley et a1 June 6, 1939

1. THE METHOD OF SEPARATING A WAX-CONTAINING MIXTURE INTO FRACTIONS OFHIGHER AND LOWER MELTING POINT, WHICH COMPRISES COUNTERCURRENTLYCONTACTING SAID WAX-CONTAINING MIXTURE IN AN EXTRACTION ZONE WITH ANEXTRACTION SOLVENT AND SOLVENT ADDITIVES AT A TEMPERATURE SUCH THAT TWOIMMISCIBLE LIQUID PHASE ARE FORMED, ONE COMPRISING THE HIGHER MELTINGWAX FRACTION CONTAINING SOLVENT AND ADDITIVES, AND THE OTHER COMPRISINGSOLVENT AND ADDITIVES AND THE LOWER MELTING WAX FRACTION, SEPARATING THEPHASES FROM ONE ANOTHER, AND REMOVING THE SOLVENT AND ADDITIVES FROMEACH, THE SOLVENT BEING INTRODUCED INTO THE EXTRACTION ZONE NEAR THEPOINT OF WITHDRAWAL OF THE HIGHER MELTING WAX FRACTION, THE FIRSTADDITIVE BEING INTRODUCED ADJACENT THE POINT OF IN-